What is EffiBEM?

Building Energy Modeling is very complex and time-consuming. It can seem completely out of your reach, or if you practice it you will still find there are many hours wasted in repetitive and cumbersome tasks, making you unable to focus on what’s really important: analyzing the outputs, evaluating Energy Efficiency Measures (EEMs) and, ultimately, using it as a powerful decision tool.

Leveraging software, EffiBEM specializes in providing new ways to streamline your workflows and create new tools that work with limited inputs for your specific applications. We also offer support and training services on BEM simulation engines.

Thus, EffiBEM puts the power of Building Energy Modeling in your hands.

What we do

EffiBEM offers all services around Building Energy Modeling, and energy efficiency in general.

BEM & Software Expertise

Workflow improvement

Tired of seeing how many hours are wasted in repetitive and cumbersome tasks, making you unable to focus on what’s really important: analyzing the outputs, evaluating Energy Efficiency Measures (EEMs).
Because we know both BEM and software, we can help you streamline your workflows so you can finally start using BEM as the powerful decision tool it can be.

Custom tools

If you have a specific application in mind, we can build you robust applications so you can plug information in and get valuable output the other way in a quick and efficient manner.
For example, when you want to use a set of limited input, populate a BEM model with smart defaults, evaluate lots of EEMs, and generate useful and pretty reports, it's a problem that we can solve with computers!

EnergyPlus and OpenStudio Support / Debugging

Ever been stuck on a ** Fatal ** Error for days at a time, unable to find what's causing it and getting dizzy looking at thousands of lines of text?
Or maybe you're unsure how to model a new strategy or product and need expert help? We fix and debug your models!

EnergyPlus and OpenStudio training

The learning curve of EnergyPlus and OpenStudio is steep. EffiBEM can ease you into it, build your skills, or gain advanced mastery of these tools. Whether you are a beginner, intermediate, or advanced user, or if you want to learn how to integrate software programming into the mix, we can tailor a solution to your needs.

Project Solutions

Energy Modeling

We can offer simulation services for all building sizes and types (multifamily, offices, mall, datacenter, etc.).
We will model according to your end goal:

  • Compliance, including ASHRAE 90.1 studies
  • Certification: LEED, BREEAM, HQE
  • Energy Simulation aided Building Design: parametric studies and optimization algorithms

Specific studies and third party review

When there is a lot at stake, having someone else chime in is valuable.

As an owner or a mechanical engineer, you might want someone to complete a comfort study, or use BEM to verify the sizing of your HVAC system.
As a BEM practitioner, a fresh look by a third party can both help you deliver the highest quality to your client, mitigate the risk of overlooking something, and help you better your skills.

EffiBEM combines BEM and Software

Most problems our industry faces today can be solved using computers

About Us

We believe that we can make you more efficient in your use of Building Energy Modeling.

We live at the intersection of BEM and software.

BEM Expertise

Start with a strong knowledge of building physics.

Add some extensive experience auditing and modeling various building types

Layer an in-depth comprehension of the inner workings of BEM software such as EnergyPlus and OpenStudio

  • Envelope
  • HVAC
  • Controls
  • Renewable Energy

Software Skills

We know software. We have a knowledge of many different technologies: Python, Ruby, VBA, C++, Web (HTML, CSS, jS).

And we know BEM-specific software: OpenStudio SDK, openstudio-standards, Eppy, etc.

We contribute to the development of open-source projects such as OpenStudio, openstudio-standards, EnergyPlus

  • General Software
  • BEM-Specific Software

Our Process

To ensure we deliver the highest quality, we think ahead in the early phases, and we test our product before we deliver it.
We also use test-driven development whenever appropriate.













Who we are

Currently a one-person team, EffiBEM has a network of highly skilled professionals it could bring in if your needs call for it.

Julien Marrec


Julien has extensive experience in energy efficiency and BEM.

Energy engineer by trade, experienced in both existing buildings and new construction. Interests include: building energy modeling, coding (Python, ruby, C++, VBA), dataviz, machine learning, etc.


Energy Efficiency
OpenStudio API

Key points

I am deeply passionate about the environment, hard science and solving complex problems. I use those attributes every day to pave the way for better, greener buildings.

I have more than 6 years experience in the energy efficiency field. I have spent 3 years working on Existing Buildings and 3 in New Construction, BEM was involved in both cases.
Because I've started by being heavily exposed to field work, I'd like to think I am able to see the bigger picture when working on New Construction.

I've always used code to streamline workflows as I hate repetitive tasks. Initially I was building most things using Excel, Word and VBA, and I transitioned a lot of it to higher-level, more versatile programming languages such as Python. Contributing to the development of OpenStudio made me learn ruby and gain exposure to C++

Open Source Software development:

As can be seen on my GitHub, I believe in giving back to Open Source. In addition to releasing some of my own tools, I also contribute to:

Q&A / Education

I am very active in the energy modeling community, both asking and answering questions on the following:

Ecole des Mines de Saint-Etienne

M.Sc. 2010
Ingénieur Civil des Mines, Double-major Master of Science in Engineering and Management

Get in Touch

We want to hear about your next project, drop us a line!

Contact Info

Located in Lorient, France
Available worldwide
P: +33 (6) 95 14 42 13
E: contact